Modern communication and radar applications often involve positioning and ranging determinations. These applications typically seek to ascertain the range between two locations, for example between a radar station and a target, between two mobile stations, or between a base station and a mobile station. Other applications seek to determine the absolute or relative position of a target or a location.
Current positioning and ranging techniques suffer from a number of undesirable characteristics. For example, Global Positioning Satellite, or GPS, presently has a resolution limited to a few feet. Moreover, GPS systems rely on expensive, sophisticated satellites orbiting the earth. Thus, ranging and positioning applications that use GPS depend on the availability of the satellites and the signals that the satellites provide. In indoor areas, for example, GPS equipment typically cannot receive satellite signals and, thus, cannot provide reliable ranging and positioning information.
To overcome the shortcomings of GPS systems, other ranging and positioning systems use radar techniques. Radar systems usually transmit a signal that includes a plurality of pulses and, by timing the arrival of a signal reflected from a target, determine the range or position of a target. Those radar systems, like GPS systems, have a limited resolution. To provide improved resolution, some ranging and positioning systems use a single pulse. Proper and reliable operation of those systems, however, depends on their ability to distinguish the first pulse that may include information about the range, position, or both, of a target. Unfortunately, no known reliable techniques exist for detecting the direct-path signal and, thus, for determining the range, position, or both, of a target accurately and with improved resolution.